A construction machine, such as an excavator, a bulldozer, a dump truck, or a wheel loader, is provided with a hydraulic pump, which is driven by an engine, in order to supply operation oil to a hydraulic actuator, which is used to actuate a working machine or a vessel. For example, Patent Literature 1 discloses control of lowering an engine speed, not limiting a pump absorption torque, when a hydraulic pump reaches a relief state in connection with driving a hydraulic pump by a diesel engine.